1. Field of the Invention
The present invention relates to an image recognition method.
2. Description of the Related Art
In the case of picking up workpieces that are loosely piled with a robot and the like, it is necessary to accurately detect a position and a posture of the workpiece positioned in the uppermost region. In such case, conventionally, the workpiece to be picked is detected using a two-dimensional gray image from a CCD camera and performing pattern matching.
For example, U.S. Pat. No. 7,177,459 discloses a method of detecting a position and a posture of workpieces that are loosely piled using a pattern matching. In this method, first, an image of the loosely piled workpieces photographed by a two-dimensional CCD camera is matched with contour shapes of the workpiece preliminarily photographed from a plurality of directions, so as to obtain a relative posture of the workpiece and the CCD camera. Thereafter, on the basis of the obtained relative posture, the position and posture of the workpiece is measured by a three-dimensional visual sensor, which is moved to a position and posture capable of clearly grasping the characteristics of the target workpiece. By doing so, it becomes possible to accurately measure the position and posture of the workpiece.
Further, U.S. Pat. No. 8,150,165 discloses dividing a photographed image of a workpiece into icons (patches), and tagging a relative positional relationship between each icon.
However, in the photographed image in the state where a plurality of workpieces is complexly overlapped, the change of luminance in the image becomes random and the characteristics become ambiguous. Therefore, there are cases where the extraction of the contour shape is not possible by the pattern matching method, and so that the identification of the accurate position and posture of the workpiece is not possible.